The present invention relates to a light weight golf ball. More particularly, it relates to a light weight golf ball having excellent flight performance and good shot feel.
It is generally considered that golf balls have longer flight distance with increasing a weight thereof, and the upper limit value of the weight is only established in accordance with regulations for golf balls. However, since golf balls having large weight tend to have poor shot feel, there has been an attempt of softening the golf balls. On the other hand, golf balls having small weight, which have short flight distance, but have excellent shot feel, have been known as xe2x80x9ca light weight golf ballxe2x80x9d.
In a case of golf balls used at driving ranges for practicing golf, in which golf balls are hit facing a water surface of a lake, since it is further required for the golf balls to float on water in order to easily collect the golf balls after hitting, it is a necessary condition for the golf balls to have a specific gravity of less than 1.0. The golf ball is an example of particularly light golf ball in the light weight golf balls. The light weight golf balls are typically classified into a one-piece golf ball consisting of Integrally molded rubber material, and a two-piece golf ball consisting of a solid core of rubber material as a main component and a cover covering on the solid core, in the same manner as typical solid golf balls. The one-piece golf ball is frequently used at driving ranges, because it has excellent durability. The two-piece golf ball is frequently used as a golf ball for a round game, since it has excellent rebound characteristics. The light weight golf ball as a golf ball for a round game has been generally approved of or employed by non-muscular players, such as feminine players, junior players and the like, in order to accomplish good shot feel and low impact force.
Present one-piece golf balls mainly used at driving ranges have excellent durability, and have large deformation amount (compression) at the time of hitting in order to accomplish soft and good shot feel. However, since the golf balls have large deformation amount at the time of hitting, it is problem that the shot feel is heavy and poor.
Recently, it has been required also for the golf balls for driving ranges to have excellent performance nearly as good as golf balls for round games. Therefore so-called two-piece golf ball, which is formed by covering a cover, has been employed as a golf ball using at driving ranges for practicing golf, in which golf balls are hit facing water surface. A two-piece golf ball for the driving ranges, which has low specific gravity and floats on water, and has good shot feel nearly as good as golf balls for round games, is proposed (Japanese Patent Kokai Publication No. 327791/1994 and the like).
However, in the conventional light weight golf balls, since the flight distance is largely reduced by decreasing a weight of the golf ball, the weight is adjusted to not less than 40 g. Therefore the golf balls are yet heavy, and shot feel is not sufficiently obtained for non-muscular players, such as feminine players, junior players and the like.
A main object of the present invention is to provide a light weight golf ball having excellent flight performance and good shot feel.
According to the present invention, the object described above has been accomplished in a two-piece golf ball comprising a core and cover by adjusting a flexural modulus of the cover, a specific gravity of the golf ball, a deformation amount of the golf ball when applying from an initial load of 98 N to a final load of 1275 N and a ratio (F/D) of the flexural modulus of the cover (F) to the deformation amount of the golf ball (D) to specific ranges, thereby providing a light weight golf ball having excellent flight performance and good shot feel.
The present invention provides a light weight golf ball comprising a core and a cover covering the core, wherein
the cover has a flexural modulus (F) of 200 to 600 MPa,
the golf ball has a specific gravity of not less than 0.50 and less than 1.00, and a deformation amount (D) of 3.1 to 5.0 mm when applying from an initial load of 98 N to a final load of 1275 N, and
a ratio (F/D) of the flexural modulus of the cover (F) to the deformation amount of the golf ball (D) is within the range of more than 50 and not more than 125.
In the golf ball of the present invention, soft and good shot feel at the time of hitting by non-muscular players, such as feminine players, junior players and the like, is accomplished by adjusting a weight of the golf ball to less than that of a conventional light weight golf ball, and the reduction of the flight distance thereby is compensated by optimizing a flexural modulus of the cover, which represents a hardness thereof. Therefore a light weight golf ball having excellent flight performance and good shot feel is accomplished.
In the golf ball of the present invention, it is required for the golf ball to have a specific gravity of not less than 0.50 and less than 1.00, preferably 0.80 to 0.99, more preferably 0.90 to 0.98, by which the weight of the golf ball is determined. When the specific gravity is not less than 1.00, the weight of the golf ball is large, and the shot feel is heavy and poor. On the other hand, when the specific gravity is less than 0.50, the weight of the golf ball is small, which reduces the flight distance. In addition, the directional stability is degraded, and it is disadvantage to round play in strong wind.
In the golf ball of the present invention, it is required for the cover to have a flexural modulus of 200 to 600 MPa, preferably 300 to 500 MPa, more preferably 300 to 400 MPa. When the flexural modulus is lower than 200 MPa, sufficient flight distance is not obtained. On the other hand, when the flexural modulus is higher than 600 MPa, the cover is too hard, and shot feel is poor.
In the golf ball of the present invention, it is required for the golf ball to have a deformation amount (ball compression) of 3.1 to 5.0 mm when applying from an 5 initial load of 98 N to a final load of 1275 N, and the deformation amount is preferably 3.3 to 4.5 mm, more preferably 3.4 to 4.0 mm. When the deformation amount is smaller than 3.1 mm, the golf ball is too hard, and the shot feel is poor. On the other hand, when the deformation amount is larger than 5.0 mm, the golf ball is too soft, and the shot feel is poor. In addition, the rebound characteristics are degraded, and sufficient flight distance is not obtained.
In the golf ball of the present invention, a ratio (F/D) of the flexural modulus of the cover F (MPa) to the deformation amount of the golf ball D (mm) when applying from an initial load of 98 N to a final load of 1275 N is noticed, and it is required for the golf ball to have the ratio (F/D) of more than 50 and not more than 125, preferably 55 to 120, more preferably 65 to 110, most preferably 80 to 95. When the ratio (F/D) is not more than 50, the golf ball is soft and flexural modulus of the cover is low, and sufficient rebound characteristics are not obtained, which reduces the flight distance. On the other hand, when the ratio (F/D) is more than 125, the golf ball is hard and the cover is hard, and the shot feel is poor.